Expansion anchors are used to attach various members such as fittings to stony structures made of concrete or the like, as in the case where various members are suspended from the inner surface of a tunnel, for example. There are various types of expansion anchors. In general, the tip end of a hollow shaft (anchor body) is divided by a plurality of circumferentially separated longitudinal slits to provide an radially expansive portion (expansion portion), and the radially expansive portion is bulged utilizing a wedging action caused by screwing of a bolt.
There is also an expansion anchor of the type that utilizes, instead of a bolt, a pin with a tapering tip portion having a progressively decreasing diameter toward the tip end. In this case, the pin is impacted with a hammer for insertion into the hollow shaft.
There is also a proposal in which an anchor body is expanded indirectly instead of being directly expanded with a bolt. In one example shown in Patent Document 1, a ball made of metal is inserted into a radially expansive portion for bulging the radially expansive portion due to an expanding action caused by the ball. Patent Document 2 also discloses a similar configuration. Patent Documents 3 and 4 disclose use of a fusiform member as a radially expanding member instead of the ball.